Tire grooving apparatus

ABSTRACT

A tire grooving apparatus according to the present invention consists of a movable carriage (3) adapted to be moved at least in the direction parallel with a tire support shaft (21), a vertically movable block (32) provided on the carriage (3) and adapted to be moved freely in the vertical direction, and a pivotable arm (4), provided on the block (32), having a cutter support unit (5) at the free end portion thereof. The cutter support unit (5) of the invention is movable up and down independently of movable block (32). As the cutter support unit (5) which is attached to the free end portion of the pivotable arm (4) can be so moved up and down independently, the depth of a tread pattern groove can be adjusted and a cutting position of a cutter (6) set arbitrarily, without replacing the cutter (6), without moving the block (32) vertically and without need of a program for correcting the quantity of movement of the cutter.

DESCRIPTION

1. Technical Field

The present invention relates to a tire grooving apparatus, and moreparticularly relates to a tire grooving apparatus, wherein a cuttersupport can be moved up and down independently, so as to carve treadgrooves having various depths by means of a cutter of the same shape andsize.

2. Background Art

Conventionally, the work of grooving a tire for trial manufacturing andlimited scale production, namely carving the tread pattern grooves inplain cured tires without any tread pattern is generally performed bymeans of a hand cutter, and it requires skill and a lot of time.

Taking the above-mentioned problems into consideration, the presentapplicants have already proposed a tire grooving apparatus having, asmain constructive features, a cutting device attached to a laterallymovable carriage which is moved in parallel and perpendicular directionsagainst the tire support shaft; a pivotable arm support shaft which isextended from the carriage; a pivotable arm attached to the supportshaft; a cutter holder which is pivotably attached to the pivotable armperpendicular to the axis thereof; a cutter which is held by the endportion of the cutter holder; and the cutting position of the cutterarranged to be on the extended axis of the support shaft (JapaneseUnexamined Patent Publication No. 54240/1988 and 177232/1986).

In the present specification, the cutting position of cutter means apeculiar point of cutter which is a certain distance (M) (includingzero) from the bottom end of the cutter holder (refer to FIG. 3).

The carving of tread pattern grooves for plain tires utilizing the tiregrooving apparatus is carried out by setting the cutting position to thetangential line (Processing Standard Point for Tread) of plain tire.Thus, since the cutting position of the cutter is kept always on theextended axis of the pivotable arm support shaft, namely on thetangential line of the plain tire, calculation of quantity of movementof the movable carriage and the pivotable arm becomes simple,programming of computer programs becomes easy and accurate groovingbecomes possible. However, when different depth of tread patterm groovesare carved by the tire grooving apparatus, for example, to carve deepergrooves, it is necessary for the cutter to be changed for a cutter oflonger effective length. On the other hand, when shallow depth groovesare carved, it is necessary for the cutter to be changed for a cutter ofshorter effective length. This produces a problem that the operation ofthe tire grooving apparatus is not easy. Moreover, if different depth oftread pattern grooves are carved without changing the cutter,displacement occurs between the cutting position and the processingstandard point for the tread (refer to FIG. 8B). In such a condition, ifa groove whose center line is parallel to the center vertical line ofthe tire tread is carved in zigzag on the tire plane, the zigzag pitchesof the grooves become different from one another. When grooves whosevertical center line inclined to the center vertical line of tire treadare carved, it is not possible to maintain carving accuracy since thecenter of the groove does not coincide with the processing standardpoint of the tread. Accordingly, it is necessary to adjust the quantityof movement of the cutter in accordance with the degree of differencebetween the cutting position of cutter and the processing standard pointof the tread. In this case, there is the problem that the controlprogram for cutter movement becomes complicated.

It is thus an object of the present invention to solve theabove-mentioned problems and to provide a tire grooving apparatus,wherein the cutter support unit is moved up and down independently, soas to carve grooves having various depths by using a cutter of the sameshape and size.

SUMMARY OF THE INVENTION

A tire grooving apparatus of the present invention comprises;

(a) a tire support shaft which rotatably supports a tire,

(b) a cutter support unit which is independently movable in the verticaldirection,

(c) a pivotable arm which holds the cutter support unit at the free endportion thereof,

(d) a vertically movable block having a rotatable shaft which pivotablyholds the pivotable arm, and

(e) a movable carriage which holds the vertically movable block in sucha manner which allows the block to move vertically and which can be atleast moved in the transverse direction which is parallel with the tiresupport shaft.

In the tire grooving apparatus of the present invention, since thecutter support unit which is moved up and down independently is attachedto the free end portion of the pivotable arm, the depth of a treadpattern groove can be adjusted and a cutting position of a can be cutterset arbitrarily without moving the block vertically and without changingcutters and without the need of a program for correcting the quantity ofmovement of the cutter.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are notlimitative of the present invention, and wherein:

FIG. 1 is a side view of a tire grooving apparatus of one embodiment ofthe present invention;

FIG. 2 is a front view of the tire grooving apparatus shown in FIG. 1;

FIG. 3 is a partially enlarged view of the cutter support unit of thegrooving apparatus shown in FIG. 1;

FIG. 4 is a sectional view taken along the line I--I of FIG. 3;

FIG. 5 is a partial sectional view of the cutter support unit for thegrooving apparatus of another embodiment of the present invention;

FIG. 6 is a side view of a conventional tire grooving apparatus;

FIG. 7 is a front view of the grooving apparatus shown in FIG. 6; and

FIGS. 8A and 8B are explanatory illustrations of the cutter positionduring carving.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention is described in detail based on thedrawings.

In FIGS. 1 and 2, numeral 1 indicates a base, numeral 2 indicates a tiresupport unit, numeral 3 indicates a laterally movable carriage, numeral4 indicates a pivotable arm, numeral 5 indicates a cutter support unit,numeral 6 indicates a cutter and numeral 7 indicates a tire.

The tire support unit 2 is fixed on the base 1, equipped with the tire 7on the tire support shaft 21 and rotates through a reduction gear (notshown) by a motor 22. Numeral 23 indicates a tire clamping handle.

The laterally movable carriage 3 is moved in the transverse directionparallel with the tire support shaft 21 (in Y-axis direction) on rail 31parallel with the tire support shaft 21 by means of a motor and a screwwhich are not shown. Numeral 32 is a vertically movable block which issupported by the laterally movable carriage 3 and is moved along guideshafts 33 in the vertical direction (in Z-axis direction) through a ballscrew in which the screw shaft is rotated by a motor 34.

Moreover, the laterally movable carriage 3 may be moved perpendicularlyto the axis of the tire support shaft 21, namely in the back and forthdirection to the tire 7 (in the X-axis direction) on rails 36 in thebase 1 along a guide bar 37 by means of a motor and a screw shaft (notshown), and thereby the degree of freedom in movement can be increasedat the time of grooving a large size tire.

A pivotable arm support shaft 38 extended from the side of verticallymovable block 32 has the axis 39, which coincides with the cuttingposition P of cutter, which moves on the cutter along the Z-axisdirection accompanying with the up and down movement of the cutter inthe X-axis direction perpendicularly to the tire support shaft 21,wherein the shaft is rotated around the axis 39 through a reduction gear(not shown) in the direction indicated by an arrow A in FIG. 2 by amotor (not shown) in the vertically movable block 32 so as to regulatethe direction of the cutter 6 with a desired angle to coincide with thecurved surface of the tire tread. It is particularly desirable that theaxis 39 should coincide with the tangential line of a plain tire.

When the cutting position of cutter coincides with the axis 39 of thepivotable arm support shaft 38 as described above, since the cuttingposition coincides with the moving center, the quantity of movement ofthe cutter tip is calcualted only by multiplying the rotated angle bythe distance from the cutting position of the cutter to the tip, and theprogram control can be easily performed by a computer.

Hereinafter, the cutter support unit 5 is described in detail.

As shown in FIGS. 3 and 4, the cutter support unit 5 comprises a cuttersupport unit body 51, a rotatable shaft 52 extended from the bottom ofthe body 51, a cutter holder 53 connected with the lower end of therotatable shaft 52, support pieces attached perpendicularly to the sidefacing the pivotable arm and a vertically movable mechanism 55. Thevertically movable mechanism 55 comprises a U-shaped framework element59 having a screw shaft 56 and a guide shaft 58. The free end portion ofthe pivotable arm 4 is fixed on the surface opposite to the screw shaft56 in the framework element 59. Two support pieces 54 are shown in FIG.3, but the number of the support piece 54 is not limited to 2. If it islarge enough to support the weight of cutter support unit 5 and move thecutter support unit 5 in the vertical direction with desired accuracy, asupport piece 54 is adoptable. The support pieces 54 have a tapped holeand a penetrated hole as shown in FIG. 4. The tapped hole engages withthe screw shaft 56, and the guide shaft 58 is inserted into thepenetrated hole. Since the screw shaft 56 is required to position thecutter support unit with high accuracy, for example, within 0.1 mm, aball screw is used. The screw shaft 56 is driven through a reductiongear (not shown) by means of that motor 57 controlled by a positionadjustment program or by a digital switch provided separately which isconnected with the upper end of the screw shaft. As to the motor 57, aservo motor is used for high accuracy control. The screw shaft 56 isrotated a desired number of times by the servo motor 57, and thereby thecutter support unit 5 independently is moved in the up (down) directionby a predetermined quantity and adjusts the carving depth of the cutter6 attached to the lower end portion of the cutter support unit 5. Thecutting position of the cutter moves in the up (down) directionaccording to the down (up) movement of the cutter 6, so that it alwayscoincide with the axis of the shaft 39. Accordingly, the carving depthcan be changed easily, and accurate tread patterns can be formed.

Moreover, the rotatable shaft 52 is rotated through a reduction gear inthe direction indicated by an arrow B by a motor which is provided inthe cutter support unit body 51 (refer to FIG. 3), and thereby changesthe direction of the cutter 6 held in the cutter holder 53, so thatdesired tread patterns can be formed.

FIG. 5 is a sectional view of the main part of another embodiment of thepresent invention. In the embodiment shown in FIG. 5, a cutter supportunit 5A is similarly held by a pivotable arm 4. Namely, the side of thecutter support unit body 51A is fixed to the free end portion ofpivotable arm 4. A box body 54A is contained in the body 51A. A supportelement 541 is provided near the center of the internal portion of thebox body 54A. A female screw element 542 and a rotating sleeve 543 aremounted on the supporting element 541. The female screw element 542engages with the screw shaft 56A which is rotatably supported by theinternal bottom of the body 51A, penetrates the box body 54A and extendsto the top surface of the body 51A. The upper end of the screw shaft 56Ais connected with a motor 57A having a reduction gear. The shape of thescrew shaft, the pitch and the motor are selected in the same manner asthe aforementioned embodiment. The screw shaft 56A is rotated by themotor 57A, whereby the box body 54A is moved in the up (down) directionalong the guide shaft 58A which is extended from the box 54A and fixedby the body 51A. When the box body 54A moves in the up (down) direction,the cutter 6 held in the cutter holder 53A which is mounted on the lowerend of the rotatable shaft 52A which is connected with the lower end ofthe rotatable sleeve 543 mounted on the box body 54A and is extendedfrom the bottom of the box body 54A and body 51A. Furthermore, therotatable sleeve 543 has a hole on which surface is provided a pluralityof longitudinally formed grooves. The spline shaft 60A extending from amotor 59A with a reduction gear from the top surface of the body 51Aengages with the grooves. When the spline shaft 60A is rotated by themotor 59A with the reduction gear, the rotatable sleeve 543 mounted onthe support element 541 through a bearing 544 is also rotated. Thedirection of the cutter 6 can be changed by rotating the rotatablesleeve 543.

As described above, in the present embodiment, the cutter 6 can be alsomoved in the vertical direction so that the cutting position alwayscoincides with the axis of shaft 39, and further the axis of shaft 39can coincide with the tangential line of the plain tire. Accordingly, inthe present embodiment, the tread patterns which have various depth ofthe grooves can also be formed accurately by means of the cutter of thesame size.

As described above, in the tire grooving apparatus of the presentinvention, since the cutter support unit can be moved up and downindependently, the depth of tread pattern grooves can be easily changed,and moreover accurate tread patterns can be formed.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

We claim:
 1. A tire grooving apparatus comprisinga tire support unitincluding a tire support shaft adapted to rotatably support a tire, acarriage, including means for moving said carriage parallel to the tiresupport shaft, a block mounted on said carriage and means operativelyconnected to said block for moving the block in the vertical direction,a block shaft extending from and rotatably supported by said block, apivotable arm member pivotably supported at one end portion by saidshaft, and a cutter supported by a cutter support unit and disposed atthe other end portion of the pivotable arm member, said cutter supportunit including means for independently moving said cutter support unitin a direction perpendicular to the axis of said block shaft extendingfrom said block to position said cutter coincident with the axis of saidshaft.
 2. The tire grooving apparatus of claim 1, wherein the means forindependently moving said cutter support unit comprises a frame memberfor supporting said cutter support unit, said frame member containing aguide shaft, a screw shaft and a motor means for rotating said screwshaft which, in turn, moves the cutter support unit in saidperpendicular direction.